Bado Classification — Monteggia Fracture-Dislocations

Overview — Monteggia Fracture-Dislocations (Adult)

The Monteggia fracture-dislocation is a fracture of the ULNAR SHAFT combined with a DISLOCATION OF THE RADIAL HEAD at the proximal radioulnar joint and/or radiohumeral joint. Originally described by Giovanni Battista Monteggia in 1814, these injuries are important because: (1) the radial head dislocation is frequently MISSED (the shaft fracture dominates attention); (2) the direction of the radial head dislocation determines the Bado type and guides reduction technique; (3) missed or chronic Monteggia injuries lead to progressive elbow deformity, loss of forearm rotation, and nerve injury. The adult Bado classification (1967) grades the injury by the direction of radial head displacement — this is directly used to plan reduction technique and surgical approach. A dedicated paediatric article (Article 159) covers the paediatric patterns and Monteggia equivalents.

The radiocapitellar rule: on ANY plain X-ray of the elbow or forearm, a line drawn through the long axis of the RADIAL SHAFT (the radiocapitellar line) must pass through the CENTRE of the capitellum on BOTH AP and LATERAL views; if this line does NOT pass through the capitellum, the radial head is dislocated — this must be diagnosed and treated regardless of what the ulna is doing; this rule applies to ALL ages; failure to apply this rule is the single most common reason for missed Monteggia injury
Adult vs paediatric Monteggia: adults almost always require operative management (internal fixation of the ulnar fracture with restoration of radial head); children may be managed conservatively if the fracture is incomplete and the radial head can be reduced (see Article 159 for paediatric management details); in adults, Type I (anterior) is the most common pattern (as in children); Type II (posterior) is significantly more common in adults than in children

Bado Classification — Adult

Bado Type	Radial Head Dislocation	Ulnar Fracture	Mechanism	Frequency (Adults)	Management
Type I — Anterior	ANTERIOR dislocation of the radial head; visible on the lateral view as the radial head displaced anteriorly relative to the capitellum; the radiocapitellar line fails to intersect the capitellum on the lateral view	Ulnar fracture with ANTERIOR angulation (apex anterior/volar angulation of the ulna)	Hyperpronation mechanism (the forearm is forced into extreme pronation, driving the radial head anteriorly while the ulna fractures with anterior angulation)	~60% of adult Monteggia injuries — the most common type	ORIF of the ulna (plate and screws — anatomical reduction of the ulna typically reduces the radial head spontaneously); if radial head does not reduce after ulnar ORIF → open reduction of the radial head (annular ligament interposition); anterolateral approach to the ulna + lateral approach to the radial head if needed
Type II — Posterior	POSTERIOR (or posterolateral) dislocation of the radial head; the radial head is displaced posteriorly relative to the capitellum; visible on the lateral view	Ulnar fracture with POSTERIOR angulation (apex posterior/dorsal); the posterior ulnar fracture may be associated with a comminuted olecranon fracture or proximal ulna fracture in adults	Axial loading on the hyperflexed elbow; direct posterior force on the proximal radius; the mechanism drives the radial head posteriorly while the ulna fractures in dorsal angulation	~15% of adult Monteggia injuries; more common in adults than children (in children, Type II is uncommon); the adult Type II is often associated with an olecranon fracture and is sometimes called the `Bado Type II`	ORIF of the ulna (olecranon plating + forearm plating for the diaphyseal component); the radial head reduction usually follows ulnar fixation; if the radial head has an associated fracture (Mason Type I/II with Bado Type II) → radial head fixation or arthroplasty as indicated; associated with the `terrible triad equivalent` pattern in some cases
Type III — Lateral	LATERAL (radial) dislocation of the radial head; the radial head displaces laterally; best seen on the AP view (the radial head is laterally displaced relative to the capitellum)	Fracture of the PROXIMAL ULNA metaphysis — typically a fracture of the olecranon or the proximal ulna shaft near the metaphyseal-diaphyseal junction; the ulna fractures in the proximal region with lateral angulation	Varus stress on the extended elbow; an adduction force applied to the forearm with the elbow extended	~20% of adult Monteggia injuries (more common in children as a paediatric pattern)	ORIF of the proximal ulna fracture; lateral radial head reduction usually follows; if lateral structures are disrupted, lateral ligamentous reconstruction may be needed
Type IV — Combined	ANTERIOR dislocation of the radial head (same as Type I) + BOTH bones of the forearm fractured — the radius shaft is also fractured in addition to the ulna shaft (both-bones forearm fracture + radial head dislocation)	BOTH ulnar AND radial shaft fractures proximal to the radial head dislocation	High-energy combined mechanism	~5% of adult Monteggia injuries; the rarest type; very high-energy mechanism; important to recognise both the shaft fractures AND the radial head dislocation	ORIF of BOTH forearm bones (separate plates for the radius and ulna) + radial head reduction (usually follows anatomical restoration of length and alignment of both bones); very demanding surgery

Management Principles — Adult Monteggia

The golden rule: in adults, ALL Monteggia injuries require ORIF of the ulnar fracture; unlike children (where a greenstick or plastic bowing ulna can sometimes be reduced by closed manipulation), the adult ulna requires internal fixation because: (1) the adult ulna does not remodel; (2) closed reduction is not maintained; (3) anatomical restoration of ulnar length and alignment is the only reliable way to achieve and maintain radial head reduction; the standard implant for adult ulnar shaft fixation in Monteggia injuries is a 3.5 mm dynamic compression plate (DCP) or locking plate applied to the dorsal or posterolateral surface of the ulna (the `tension side`)
Approach to the ulna: the ulna is subcutaneous and can be approached through a single longitudinal incision over the subcutaneous border; the plate is applied along the posterior surface of the ulna; the posterior interosseous nerve (PIN — deep branch of the radial nerve) must be identified and protected during any approach to the proximal radius (it winds around the proximal radius through the radial tunnel — at risk with lateral approaches to the radial head)
When the radial head does not reduce after ulnar ORIF: if anatomical ulnar plate fixation has been confirmed but the radial head remains dislocated → OPEN REDUCTION of the radial head is required; the most common cause of failure to reduce is interposition of the annular ligament or a portion of the joint capsule between the radial head and the capitellum; open reduction via a Kocher or modified Boyd approach to the lateral elbow; meticulous inspection and removal of any interposing tissue; if the annular ligament cannot be repaired, a reconstruction using a strip of the lateral triceps fascia (Bell-Tawse technique — primarily described in children but applicable in adults for annular ligament reconstruction) may be performed

Chronic (Missed) Monteggia in Adults

Chronic Monteggia injuries (presentation >6–8 weeks from injury): significantly more complex to manage than acute injuries; soft tissue contractures around the dislocated radial head and around the elbow prevent simple reduction; the radial head may deform (flatten, become irregular) from chronic subluxation on the capitellum; management: ulnar corrective osteotomy (to restore ulnar length, bow, and alignment) + open radial head reduction + annular ligament reconstruction; for established cases with deformed radial head — radial head excision (in skeletally mature individuals) or replacement arthroplasty; this is highly complex reconstructive surgery and should be referred to a specialist elbow unit

Exam Pearls

Radiocapitellar line: a line through the radial shaft axis must pass through the capitellum on BOTH AP and lateral views; if it does NOT → radial head is dislocated → Monteggia until proven otherwise; apply to ALL forearm and elbow X-rays
Bado classification: Type I (anterior radial head, anterior ulna apex — most common 60%); Type II (posterior — more common in adults); Type III (lateral — more common in children); Type IV (both bones + anterior dislocation — rarest)
Adults = always ORIF: adult ulna cannot be managed conservatively; plate fixation of the ulnar fracture restores length and alignment → radial head usually reduces spontaneously; if it does not → open reduction for annular ligament interposition
PIN (posterior interosseous nerve) injury: most common nerve injury; neuropraxia in ~10–20%; cannot extend fingers or wrist (pure motor — deep branch of radial nerve); passes through the radial tunnel around the proximal radius; at risk during surgical approaches to the radial head; usually resolves with time (3–6 months)
Annular ligament interposition: most common reason for failure of closed/indirect radial head reduction; the annular ligament (which normally holds the radial head against the proximal ulna) becomes trapped between the radial head and the capitellum during dislocation; must be surgically excised and the annular ligament repaired or reconstructed
Type IV: both forearm bones fractured PLUS radial head dislocation; most high-energy; requires individual ORIF of both bones; do not forget to check radiocapitellar line even when both bones appear fractured
Chronic Monteggia: presents with restricted forearm rotation, pain, sometimes painless; ulnar corrective osteotomy + open radial head reduction; radial head excision or arthroplasty for deformed head; refer to specialist elbow unit

Bado Classification — Monteggia Fracture-Dislocations

References

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